Type 1, or Insulin-Dependent Diabetes Mellitus (IDDM), arises in genetically predisposed individuals as a result of immune mediated destruction of the pancreatic islet insulin secreting B-cells. It is now possible to identify individuals at high risk for future progression to IDDM, using a combination of genetic, immunologic and metabolic screening tests. The major objective of the DPT-1 is to determine whether intervention by antigen based therapies in non-diabetic relatives of persons with IDDM will delay or prevent their development of the disease. This study is part of a multi-center trial funded by the National Institutes of Health.